Biological fluids are routinely analyzed in hospital clinical laboratories to aid in the diagnosis of disease and to provide critical information about a patient's well-being. The constituents of blood, lymph, urine, or products derived therefrom provide meaningful patient health information to a clinician or physician. Since physicians are becoming increasingly dependent on clinical laboratory analyses for the diagnosis of disease and the monitoring of therapy, improved reliability and efficiency of these procedures is mandatory. Automation of the chemical analysis of biological fluid constituents has solved a great many of the problems associated with conducting reliable and efficient analyses; however, automated analysis has created its own dilemmas for the clinician. Since the handling and processing of a large number of fluid samples on a continuous basis with a rapid turnaround or completion time is required, many of the automated clinical analyzers presently available have been designed to monitor the chemical analyses rapidly. However, the processing of the biological fluid and its manipulation prior to delivery to the analyzer significantly retards the rate of the overall analysis. The processing and manipulation steps generally include the centrifugation of blood or filtration of biological fluids followed by serial dilutions and transfer to a cuvette or sample container.
Biological fluids, such as blood, are usually collected in a standard collection tube. Conventional blood collection tubes used in many hospitals and clinics are elongated cylindrical containers having an opening at one end fitted with a resilient stopper, and a rounded or flat bottom at the other end. The most common size of these blood collection tubes accommodates 10 milliliters of blood or other biological fluid. Illustrative of such blood collection tubes is the VACUTAINER* brand sold by Becton-Dickinson (*Registered Trademark of Becton-Dickinson). A phlebotomist first obtains a specimen of a patient's blood, appropriately labels the patient's specimen, and delivers the specimen to the clinical laboratory for analysis. The plasma or serum derived therefrom is processed and analyzed either manually, semi-automatically, or automatically. In the majority of cases, the specimen must first be dispensed from the collection tube to a sample test tube or cuvette as described above.
Furthermore, in certain instances where only minute quantities of biological fluid are available for analysis, such as in pediatric or geriatric analysis, the fluid cannot be collected and stored in large specimen tubes as described above because the sample level in such containers would not be adequate for retrieval prior to analysis. Such small quantities of fluids also have a tendency to significantly evaporate when stored in large containers, thus concentrating the chemical and enzymatic constituents therein. This results in erroneous analytical results and could possibly affect the diagnosis and treatment given the patient. Therefore, it is necessary to employ small-volume containers which inhibit evaporation for the storage and delivery of minute fluid samples in the clinical chemistry laboratory. Although various fluid-containers are available for this purpose, their small overall size and shape make handling extremely cumbersome. Furthermore, their use in conventional storage racks or those designed for loading into automatic chemical analyzers is precluded because of their small dimensions.
Certain automated chemical analyzers are capable of utilizing standardized conventional specimen containers as a means for introducing a patient's specimen into the analyzer. However, they are not equipped to handle specimen containers designed to hold small quantities of fluid. Therefore, one such instrument manufacturer requires that a separate sample cup be placed in the top of a standard-sized 10 milliliter collection tube for withdrawal of specimen and delivery to the analyzer. This creates several drawbacks for the rapid and reliable processing of a patient's specimen. One problem being the additional error-prone and time-consuming step of transferring the specimen from the specimen container to the sample cup, and another being the size requirements of the sample cups which contributes to significant evaporation of smaller fluid samples and which do not permit handling of small or micro quantities of fluid sample. Arrangements such as this are also prone to sample spillage due to dislodgements of the sample cup from the top of the container.
Heretofore, a micro-container for holding minute quantities of biological fluids, which could simultaneously be easily manipulated and employed in both conventional and automatic storage racks, has not been available.